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.TH T_LOOK 3NSL "May 7, 1998"
.SH NAME
t_look \- look at the current event on a transport endpoint
.SH SYNOPSIS
.LP
.nf
#include <xti.h>



\fBint\fR \fBt_look\fR(\fBint\fR \fIfd\fR);
.fi

.SH DESCRIPTION
.sp
.LP
This routine is part of the \fBXTI\fR interfaces which evolved from the
\fBTLI\fR interfaces. \fBXTI\fR represents the future evolution of these
interfaces. However, \fBTLI\fR interfaces are supported for compatibility. When
using a \fBTLI\fR routine that has the same name as an \fBXTI\fR routine, the
\fBtiuser.h\fR header file must be used.  Refer to the  \fBTLI\fR
\fBCOMPATIBILITY\fR section for a description of differences between the two
interfaces.
.sp
.LP
This function returns the current event on the transport endpoint specified by
\fIfd\fR. This function enables a transport provider to notify a transport user
of an asynchronous event when the user is calling functions in synchronous
mode. Certain events require immediate notification of the user and are
indicated by a specific error, \fBTLOOK\fR, on the current or next function to
be executed.
.sp
.LP
This function also enables a transport user to poll a transport endpoint
periodically for asynchronous events.
.SH RETURN VALUES
.sp
.LP
Upon success, \fBt_look()\fR returns a value that indicates which of the
allowable events has occurred, or returns zero if no event exists. One of the
following events is returned:
.sp
.ne 2
.na
\fB\fBT_LISTEN\fR \fR
.ad
.RS 17n
Connection indication received.
.RE

.sp
.ne 2
.na
\fB\fBT_CONNECT\fR \fR
.ad
.RS 17n
Connect confirmation received.
.RE

.sp
.ne 2
.na
\fB\fBT_DATA\fR \fR
.ad
.RS 17n
Normal data received.
.RE

.sp
.ne 2
.na
\fB\fBT_EXDATA\fR \fR
.ad
.RS 17n
Expedited data received.
.RE

.sp
.ne 2
.na
\fB\fBT_DISCONNECT\fR \fR
.ad
.RS 17n
Disconnection received.
.RE

.sp
.ne 2
.na
\fB\fBT_UDERR\fR \fR
.ad
.RS 17n
Datagram error indication.
.RE

.sp
.ne 2
.na
\fB\fBT_ORDREL\fR \fR
.ad
.RS 17n
Orderly release indication.
.RE

.sp
.ne 2
.na
\fB\fBT_GODATA\fR \fR
.ad
.RS 17n
Flow control restrictions on normal data flow that led to a \fBTFLOW\fR error
have been lifted. Normal data may be sent again.
.RE

.sp
.ne 2
.na
\fB\fBT_GOEXDATA\fR \fR
.ad
.RS 17n
Flow control restrictions on expedited data flow that led to a \fBTFLOW\fR
error have been lifted. Expedited data may be sent again.
.RE

.sp
.LP
On failure,  -1 is returned and \fBt_errno\fR is set to indicate the error.
.SH VALID STATES
.sp
.LP
ALL - apart from \fBT_UNINIT\fR.
.SH ERRORS
.sp
.LP
On failure, \fBt_errno\fR is set to one of the following:
.sp
.ne 2
.na
\fB\fBTBADF\fR\fR
.ad
.RS 11n
The specified file descriptor does not refer to a transport endpoint.
.RE

.sp
.ne 2
.na
\fB\fBTPROTO\fR\fR
.ad
.RS 11n
This error indicates that a communication problem has been detected between XTI
and the transport provider for which there is no other suitable XTI error
\fB(t_errno)\fR.
.RE

.sp
.ne 2
.na
\fB\fBTSYSERR\fR\fR
.ad
.RS 11n
A system error has occurred during execution of this function.
.RE

.SH TLI COMPATIBILITY
.sp
.LP
The \fBXTI\fR and \fBTLI\fR interface definitions have common names but use
different header files. This, and other semantic differences between the two
interfaces are described in the subsections below.
.SS "Interface Header"
.sp
.LP
The \fBXTI\fR interfaces use the header file, \fBxti.h\fR. \fBTLI\fR interfaces
should \fInot\fR use this header.  They should use the header:
.sp
.in +2
.nf
#include <tiuser.h>
.fi
.in -2

.SS "Return Values"
.sp
.LP
The return values that are defined by the \fBXTI\fR interface and cannot be
returned by the \fBTLI\fR interface are:
.br
.in +2
\fBT_GODATA\fR
.in -2
.br
.in +2
\fBT_GOEXDATA\fR
.in -2
.SS "Error Description Values"
.sp
.LP
The \fBt_errno\fR value that can be set by the \fBXTI\fR interface and cannot
be set by the \fBTLI\fR interface is:
.br
.in +2
\fBTPROTO\fR
.in -2
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7)  for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
MT Level	Safe
.TE

.SH SEE ALSO
.sp
.LP
.BR t_open (3NSL),
.BR t_snd (3NSL),
.BR t_sndudata (3NSL),
.BR attributes (7)
